Dexlansoprazole, namely (R)-2-[[[3-mehyl-4-(2,2,2-trifluoroetoxy)-2-piridyl]methyl]sulphinyl]benzimidazole is an enantiomer of lansoprazole. Dexlansoprazole is a protonic pump inhibitor and is used in the treatment of diseases such as erosive aesophagitis, gastroesophageal reflux and gastrointestinal disorders. Dexlansoprazole is known from WO 92/08716, and disclosed in crystalline solid form in U.S. Pat. No. 6,462,058, in particular in crystalline anhydrous form (with a melting point of 147-148° C.) and sesquihydrate form (with a melting point of 76-80° C.), whereas amorphous dexlansoprazole is known from US 2009/0163553.
As disclosed in US 2004/0049045, crystalline anhydrous dexlansoprazole has a higher thermal stability than other solid forms of dexlansoprazole. The known processes for the preparation of crystalline anhydrous dexlansoprazole have a low industrial application, because of both the relevant degradation of the starting materials, due to the used reaction conditions, and the resulting low yields of crystalline anhydrous dexlansoprazole.
Thus, there is the need of an alternative, improved process for the preparation of crystalline anhydrous dexlansoprazole, easily applicable on industrial scale and with high yields.